Electromagnetic reproducer for use with gramophone and the like records



April 30, 1929.

J. B. WOODROFFE ,1 ELECTROMAGNETIC REPRODUCER FOR USE WITH GRAMOPHONE AND THE LIKE RECORDS Filed May 28, 1927 A? I) o o Patented Apr. 30, 1929.

PATENT OFFICE.

UNITED STATES JOHN BADEN WOODIROIFFE, OF LONDON, ENGLAND,

ELECTROMAGNETIC REPBODUCER FOR USE WITH GRAMOPHONE AND THE LIKE RECORDS.

Application filed May 28, 1927, Serial No. 195,080, and in Great Britain January 22, 1927.

This invention relates to electromagnetic reprodncers fornse with gramop'hone and the like records and suitable for playing such records for example, by means of a thermionic valve, amplifier and loud speaker.

Electromagnetic reproducers which may be employed either for playing gramophone or the like records by means of an amplifier and loud speaker or for controlling a radio transmitter for transmission of gramophone records, or, in some cases, for cutting records, normally comprise a magnetic circuit having a moving part adapted to carry a gramophone needle or cutting device, and one or more coils mounted upon said magnetic circuit.

The present invention has for its object to provide an electromagnetic reproducer having damping means whereby distortion shall be reduced to aminimum.

According to this invention an electromagnetic reproducer of the kind described is provided with a pivoted armature and damping means comprising one or more leather, rubber or the like straps, each of which is attached to the said armature and to some relatively fixed portion of the apparatus.

Preferably means are provided for adjusting the initial tension of the strap or straps.

Preferably also additional damping means 30 comprising rubber or the like tubes directly damping the movements of the armature are provided.

The invention is illustrated in the accompanying drawings in which Figure 1 shows one modification, Figures 2 and 3 being detail views thereof and Figure 4 a second modification.

Referring to Figures 1, 2 and 3, 1 is a U-shaped permanent magnet provided at or near the end of one limb with a U-shaped pole piece 2 on each limb of which is mounted a coil 3 the said coils being connected in series. The limbs of the pole piece are substantially at right angles to the limbs of the permanent magnet and project towards the second limb thereof. Projecting inwards from the said second limb of the magnet is an arm 4 the inward end of which carries a pivotally mounted armature 5. The said armature is in close proximity to the tips of the U-shaped pole piece, and lies substantially parallel to the limbs of the permanent magnet, the pivot 6 of the said armature being situated at a point opposite the mid-point between the limbs of the pole piece and at right angles to the common plane of the magnet and the said pole piece. A leather, rubber or similar strap or attenuate element 7 is attached at its centre to the upper end of the armature the ends of the said strap being fixed to the sides of cylindrical uprights 8 carried by an ebonite terminal plate 9 or the like, attached to the side of the magnet at the bend thereof. These uprights may be rotated and locked (by means of nuts) in any desired position, so that in effect the two halves of the strap form a pair of reins, the tension of which mav be adjusted by turning the uprights. The usual terminal board and tonearm fitting are provided upon the magnet while the lower end of the armature is formed as, or has attached to it, a stylus or cutter carrier 10. 11 are small tubular pieces of rubber or the like located in a groove 12 formed in the end of the arm 4 and between the pivots 6. The tubes 11 form additional damping means since they are between the relatively fixed arm 4 and the armature In Figure 3 which is an end view of the arm 4, the armature 5 has not been shown for the sake of clearness. 13 is a short tube for attaching the device to a gramophone tone arm.

In a modification shown in Figure 4 the U-shaped pole piece 2 of Figures 1, 2 and 3 is dispensed with and the coils are mounted each on a pole piece 2' located on either side of the pivoted armature 5,,0ne above and the other below the pivotal point 6. In this construction the armature and its pivot are carried by suitable plates 14 or by the arms of a fork formed of non-magnetic material and suitably attached to the magnet.

What I'claim is 1. An electromagnetic reproducer suitable for playing gramophone and the like records, and comprising an armature adapted to carry a stylus at one end, pivotal mounting means for said armature disposed intermediate the ends of the latter, and damping means comprising an attenuate strap attached to said armature above its pivot and adjacent its other end and to the body of the reproducer.

2. An electromagnetic reproducer suitable for playing gramophone and the like records, and comprising an armature adapted to carry a stylus at one'end, pivotal mounting means for said armature, and damping means com prising an attenuate strap attached intermediate its ends to said armature above its pivotal axis and adjacent the other end of the latter, and at the-ends of the strap of the reproducer.

3. An electromagnetic reproducer suitable for playing gramophone and the like records and comprising an armature adapted to arry a stylus at its lower end, pivotal mounting means for said armature, and dampingmeans comprising a strap attached at its centre to said'armature above its pivotal axis and adjacent the top and at its'ends to the body of the reprodiicerf i 4:. An electromagnetic reproducer suitable for playing gramop'hone and the like records,

and comprising an armature adapted to carry a stylus at lower end, pivotal mounting means "for said armature, and damping means comprising an attenuate leather strap attached to said armature above the pivotal axis thereof and tothe'body of the reproducer.

5. An electromagnetic reproducer suitable for playing'gramophone and the like records and comprising an armature, pivotal mounting means for said armature, damping means "comprising an attenuate strap attached to said armature above its pivotal axis and means on the reproducer to which the ends of the strap are fastened for adjusting the initial tension of said sti-ap i 6. An electromagnetic .reproduc'er suitable for playing 'grainophone and the like records landcompris ng anlarmature adapted to carry a stylus atiits loiver end, pivotal mounting means' for said armature,"damping means eomprising'an attenuate strap attached at its centre to said armature above said a'rmatures pivotal axis and at its ends to the body of the I projducer, and means adjacent the ends of the strapfor adjustingtheinitial tension of said strap.

comprising astrapattached at its centre to said armature and at its ends to" the body of the reproducer, and adjustable pillars mounted in the said body ofth'e reproducer for ad- Justina the initial tension of said strap. 9. in electromagnetic reproducer suitable "for playing gramo'phone and'the like records and comprising an armature, pivotal mounting means forsaid armature, damping means comprising an attenuate strapv attached to said armature above the pivotal axis thereof and to the body of the reproducer, and rubber bufi'ers between said armature and said body of the reproducer.

10. An electromagnetic reproducer suitable for playing gramophone and the like records and comprising an armature, pivotal mounting means for said armature, damping means comprising an attenuatestrap attached at its centre to said armature adjacent its top and at its ends to the body of the reproducer, and rubber butters between said armature and said body of the reproducer.

11. An electromagnetic reproducer suitable for playing gramophone and the like records and comprising an armature, pivotal mounting means for said armature, damping means comprising a strap attached at its centre to said armatureand at its ends to the body of the reproducer, adjustable pillars mounted in thesaid body of the reproducer for adjusting the initial tension of said strap, and rubber buil'ers between said armature and said body of the reproducer.

12. An electromagnetic reproducer suitable for playing gran'iophone and the like records and comprising an armature, pivotal mounting means for said armature, damping means (,(JlllPIlSlIlg a strap attached to said armature and to the body of the reproducer, and tubular rubber buii'ers between said armature and said body of the rcproducer.

13. An electromagnetic reproducer suitable for playing gramophone and the like records and comprising an armature, pivotal mountin g means for said arn'iature, damping means comprising a strap attached at its centre to said armature and at its ends to the body of the reproducer, and tubular rubber butiers between said armature and said body of the reproducer.

I '14. An electromagnetic reproducer suitablefor playing gramophone and the like records and comprising an armature, pivotal mounting means for said armature, dampingmeans comprising-a strap attached at its centre to said armature andat its ends to the body of the reproducer, adjustable pillars mounted in the said body of the reproducer for. ad

justing the initial tension of said strap, and tubular rubberbuffers between said armature and said body of the reproducer.

" 15. Incombination a magnetic frame, a

tern'iinal boardupon said frame, an armature pivotally mounted inisaid frame, a, strap a t-. ,taclied at its centre to sand armature, and at its endsto adjustablymountedpillars in said terminal board, pole pieces located on either side of said armature, one above and one below the pivotal point thereof, coils upon said pole pieces, and tubular rubber butters "between said armature and said magnetic frame.

In testimony that I claim the foregoing as my invention I have signed my name this 17th day of May, 1927.

JOHN BADEN \VOODROFFE. 

